What is Transmission MediaSending data from one device to another is called transmission of data.

Medium used to transmit the data is called Media.

Transmission of data through Medium is called Transmission Media.

Types of Transmission Media

Unguided (Wireless)Use radio or infrared signals which can travel through air.Can be used in LANS, MANS and WANS (using satellites and microwave communication).Data Transfer depend on ranges of frequencies viz. Radio range frequencies, Microwave frequencies and Infrared Range frequencies.

Wireless Transmission Frequencies1GHz to 40GHz (Microwave Frequencies)highly directionalSatellite communication

30MHz to 1GHz (Radio Range Frequencies)Omni directionalbroadcast radioDont require dish shaped antennas

3 x 1011 to 2 x 1014 (Infrared Range Frequencies)LocalUsed in remotes of electronic instruments

InfraredAllows computing devices to communicate via short-range wireless signals.

Computers can transfer files and other digital data bidirectionally.

Are blocked by walls unlike Wi-Fi and bluetooth.

No licenses required for usage.

Used in remote controls of electronic devices.

Very short range (not more than 5 metres).

Microwave FrequenciesHave higher frequency than radio waves.The frequency is in the range of 1GHz-40Ghz. The most popular applications of microwave waves are bluetooth and radar.GPS devices, microwave ovens and radio astronomy also use microwave waves.Also used in WANS.

Radio SignalsThe frequency is in the range of 30 MHz to 1 GHz.Have a longer wavelength than infrared lights.Used in mobile communication,broadcasting,radarand other navigation systems, satellite communication, computer networks and innumerable such devices.It also has its application in the medical industry.

Wi-Fi

WiFi or Wireless Fidelity refers to the technology surrounding the radio transmission of internet protocol data from an internet connection wirelessly to a host computer.

Wi-FiWi-Fi is one of the most important examples of wireless data transmission.Wi-Fi can be found at a number of places like college campus, business units, airports hospitals etc where a user can connect to the Wi-Fi connection and use internet.It uses radio signals to transfer data.Security is a very important aspect of Wi-Fi connections.Many cities like london are planning for city wide Wi-Fi by the year 2012.Based on IEEE 802.11 standardAlso known as wireless local area network(WLAN)A Wi-Fi signal occupies five channels in the 2.4GHz band. Any two channel numbers that differ by five or more, such as 2 and 7, do not overlapEffective isotropically radiated power(EIRP) in the EU is limited to 20dBm(100mW)

BluetoothBluetooth is a low-cost, low power, short range wireless communication technology used in networking, mobile phones and other portable device. Bluetooth wireless technology also enables devices to communicate with each other as soon as-they come within range; no need to connect, plug into, install, enable or configure anything.It uses short-wavelength radio transmissionsin theISMband from 24002480MHzBluetooth operates in the range of 24002483.5MHz (including guard bands). This is in the globally unlicensed Industrial, Scientific and Medical (ISM) 2.4GHz short-range radio frequency band. Bluetooth uses a radio technology calledfrequency-hopping spread spectrum. The transmitted data is divided into packets and each packet is transmitted on one of the 79 designated Bluetooth channels. Each channel has a bandwidth of 1MHz. The first channel starts at 2402MHz and continues up to 2480MHz in 1MHz steps. It usually performs 1600hops per second, withAdaptive Frequency-Hopping(AFH) enabled.[9]

Benefits of Bluetooth

Possible to connect to the Internet on a dial-up connection through mobile phone. Surfing the Internet then becomes possible anywhere your mobile phone can connect to your internet service provider.Perhaps you prefer to use a traditional mouse with your laptop. Choose a Bluetooth-enabled mouse and you wont have to keep track of a mouse cable.Transfer of data Bluetooth mobile devices and earphones.